All of these “25 random things about me” and “answer these 10 questions” chain quizzes will work very well as data mining when you’re trying to figure out the personal Q&A information used in website security systems.

HAHAH
I remember a myspace bulletin getting passed around that was very “the name of your first pet” “your mother’s maiden name” and I just went “huh, wonder who will save all of these and what kind of badness will result.”

In Cory Doctorow’s Little Brother, the evil, corrupt gub’ment used them to match the online personas of dissidents to real-life people. In fact, I seem to recall them specifically planting certain questions to help better home in on certain key facts.